Conduit Bending calculator
Parallel Roll Offset Calculator
Use this rolling offset calculator before reading the formula tables. Enter horizontal offset, vertical rise, bend angle, conduit type, and first-mark distance to calculate true travel, roll angle, mark spacing, shrinkage, and bend marks for a 3D conduit layout.
Updated August 4, 2026
Example Calculations
How to Use
Rolling Offset Calculator for 3D Conduit Layout
Start with the calculator inputs for the actual obstruction. Enter the horizontal offset, vertical rise, bend angle, conduit type, and distance to the first mark. The result gives the true travel distance, roll angle, spacing between marks, shrinkage allowance, and second-mark location for that layout.
Inputs used by the calculator
- Horizontal offset is the side-to-side movement needed to clear the obstruction.
- Vertical rise is the up-or-down movement at the same obstruction.
- Bend angle controls the multiplier and shrinkage basis used for the mark spacing.
- Conduit type and size keep the layout tied to the field material before bending.
- Distance to first mark lets the result place the second mark without a separate hand calculation.
Formula reference after using the calculator
Use these formulas to understand the calculator output after your project dimensions are entered. The formulas by themselves do not choose the layout dimensions.
| Calculation | Formula | What It Gives You |
|---|---|---|
| True Offset | √(horizontal² + vertical²) | Actual diagonal distance the conduit travels |
| Roll Angle | arctan(horizontal ÷ vertical) | How much to rotate the bender from vertical |
| Mark Spacing | True Offset × Multiplier | Distance between bend marks on the conduit |
Multipliers and Shrinkage by Bend Angle
| Bend Angle | Multiplier | Shrinkage/inch of offset | Best For |
|---|---|---|---|
| 22.5° | 2.613 | 3/16" | Gentle bends in exposed areas, large conduit |
| 30° | 2.000 | 1/4" | Most common — easy 2× multiplier for field math |
| 45° | 1.414 | 3/8" | Tight spaces, short distances |
| 60° | 1.155 | 1/2" | Very tight bends (rarely used) |
Try the HVAC duct preset in the calculator
Use the HVAC duct preset above when you want a quick model for a conduit that must move sideways and upward at the same obstruction. Load the preset, adjust the horizontal offset, vertical rise, bend angle, and first-mark distance, then use the calculator output for the bend marks.
- Confirm whether the obstruction requires movement in both planes.
- Load or edit the horizontal and vertical movement values.
- Select the bend angle you plan to use in the field.
- Use the returned mark spacing and shrinkage allowance as the layout record.
Bending sequence: Make the first bend at mark 1, rotate the conduit by the calculated roll angle, then make the second bend at mark 2 in the opposite direction. The conduit now travels diagonally through both planes.
Pro Tips for Rolling Offsets
- Mark a reference line: Draw a straight line along the full length of the conduit before bending. After making both bends, this line should be straight when viewed from the side — if it spirals, your roll angle was inconsistent between bends.
- Use a torpedo level: Tape a torpedo level to the conduit to verify the roll angle before making the second bend.
- Bend order matters: Always make the first bend first, rotate, then make the second bend. Don't try to pre-rotate before the first bend.
- Spring-back compensation: For 1" EMT and larger, add 2–3° to each bend to compensate for spring-back. Check with a protractor after bending.
- Field verification: Hold the conduit in position after the first bend to verify the roll angle is correct before making the second bend. It's much easier to adjust before bending than after.
Common Applications
More applications. Open to review 5 additional use cases.
Frequently Asked Questions
What is a rolling offset and how is it different from a regular offset?
A regular offset moves conduit in one plane — either left/right OR up/down. It's a 2D bend. A rolling offset moves conduit in both planes simultaneously, creating a 3D diagonal path. This requires rotating (rolling) the bender to an angle between the two planes. The true offset distance is calculated using the Pythagorean theorem: √(horizontal² + vertical²), which is always larger than either individual dimension. Rolling offsets are needed when an obstacle forces conduit to move both horizontally and vertically at the same point.
How do I determine the roll angle for the bender?
Roll angle = arctan(horizontal distance ÷ vertical distance). This tells you how many degrees to rotate the bender from its normal vertical position. For equal horizontal and vertical distances, the roll angle is 45°. If horizontal > vertical, the angle exceeds 45° (conduit moves more sideways). If vertical > horizontal, the angle is less than 45° (conduit moves more up/down). Use the calculator for precise values — even a 5° error in roll angle causes noticeable misalignment at the end of the bend.
Why do my rolling offsets always come out twisted or misaligned?
The most common causes are: (1) inconsistent roll angle between the two bends — both bends must be rotated the exact same amount; (2) not rotating the conduit after the first bend before making the second — you must physically rotate the pipe by the roll angle; (3) spring-back in larger conduit sizes changing the effective bend angle; (4) measuring error in the mark spacing. Fix: draw a reference line along the conduit before bending and align both bends to it. After both bends, the reference line should appear straight when viewed from the side.
Which bend angle should I use for rolling offsets — 22.5°, 30°, or 45°?
Use 30° as your default — the 2× multiplier makes field math simple and the bend is moderate in force and appearance. Use 22.5° when: the conduit is exposed (gentler, more professional look), the conduit is 1-1/4" or larger (less force required), or the offset is large. Use 45° when: space is tight and you need to cover the offset in the shortest distance. Avoid 60° bends unless absolutely necessary — they require significant force and can kink thin-wall conduit.
How do I account for shrinkage in a rolling offset?
Shrinkage in a rolling offset uses the true travel distance, not just one of the individual movements. Enter the project dimensions and bend angle in the calculator so the shrinkage allowance is tied to the same true offset and multiplier basis as the mark spacing.
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